The medicinal plant Yerba Santa, member of the Waterleaf Family, genus Eriodictyon, has a long tradition of use. Yerba Santa (including Eriodictyon californicum, Eriodictyon trichocalyx and other related species) has been used in treating respiratory conditions, including colds, cough, asthma and bronchitis. This herb has also been found effective for a number of other symptoms including gastrointestinal disorders, fatigue, rheumatism, and allergies. Biochemical analyses have confirmed Yerba Santa to have flavonoids that show promise as anti-carcinogens (Liu Y L, Ho D K, Cassady J M, Cook V M, Baird W M (1992) J Nat Prod 55:357-363).
For medical purposes, Yerba Santa has been used as either a dry herb or an extract. (Heizer R F, Elsasser A B (1980) The natural world of the California Indians, University of California Press, Berkeley & Los Angeles, Calif. 271 pp.). Many herbal stores carry different products containing Yerba Santa such as, for example, leaf powder, extracts, leaf tea, and cream. The fluid Yerba Santa extracts have been used in food, beverages, pharmaceuticals and cosmetics.
Yerba Santa is a perennial evergreen shrub (1-2 meters) that grows in dry, hilly areas of California and Northern Mexico. During dry months, the leaves become hard and resinous in order to hold and conserve water. When applied to mucosal surfaces, the herb preparation holds the aqueous component in contact with cells, reestablishing mucopolysaccharides. It is hypothesized that this property may facilitate the adherence to the mucosa of compositions such as, for example, pharmaceutical agents.
In recent years, there has been an increased interest in mass multiplication of this unique plant. In vitro culture techniques have been used successfully for large scale production of many medicinally important plant species. However, methods for in vitro propagation and tissue culture techniques for Yerba Santa have not previously been described.
Plant biotechnology has provided successful tissue culture and transformation technologies for a variety of plants. However, the use of biotechnological tools in medicinal plant science has been very limited as compared to other crops. Nevertheless, in recent years such techniques have been developed for number of important medicinal plants such as Ginkgo biloba, Digitalis lanata, Artenisia annua, Papaver somniferum, Camptotheca acuminate, Ophiorrhiza prostrate, and Mentha piperita. Although Yerba Santa is a very important medicinal plant, there have been no techniques described for in vitro propagation, cell culture cultivation, regeneration and transformation of this perennial shrub.
Modern plant biotechnology has opened new avenues for producing recombinant molecules, including, but not limited to, vaccines (Hansson M, Nygren P A & Stahl S (2000) Biotechnol Appl Biochem 32:95-107; Daniell H, Streatfield S J & Wycoff K (2001) Trends Plant Sci 6:219-226; Ma J K C, Drake P M W & Christou P (2003) Nat Rev Genet 4:794-805; Koprowski H (2005) Vaccine 23:1757-1763; Pogrebnyak N., Golovkin M., Andrianov V., Spitsin S., Smirnov Y., Egolf R., Koprowski H (2005) Proc Natl Acad Sci USA 102: 9062-9067; and Golovkin M., Spitsin S., Andrianov V., Smirnov Y., Xiao Y., Pogrebnyak N., Markley K., Brodzik R., Gleba Y., Isaacs S N, Koprowski H. Proc Natl Acad Sci USA (2007), 104: 6864-6869; Goldstein D A, Thomas J A (2004) QJ Med 97:705-716) or microbicides (O'Keefe B. et al. Proc Natl Acad Sci USA (2009), 106: 6099-6104). This approach has become an attractive alternative to other technologies since it is associated with low production cost, overall safety, and scalability potential. A potential benefit of using plants for vaccine production is the possibility of applying preparations directly to bodily surfaces such as, for example, mucosal surfaces (Goldstein D A, Thomas J A (2004) QJ Med 97:705-716; Giddings G, Allison G, Brooks D, Carter A (2005) Nat Biotechnol 18:1151-1155; Pogrebnyak N. Markley K., Smirnov Y., Brodzik R., Bandurska K., Koprowski H., Golovkin M (2006) Plant Sci. 171: 677-685); Golovkin M., Spitsin S., Andrianov V., Smirnov Y., Xiao Y., Pogrebnyak N., Markley K., Brodzik R., Gleba Y., Isaacs S N, Koprowski H. Proc Natl Acad Sci USA (2007), 104: 6864-6869; O'Keefe B. et al. Proc Natl Acad Sci USA (2009), 106: 6099-6104).